The present invention was made with U.S. Government support, and the U.S. Government has certain rights in the invention.
The present invention relates to an improved auscultation sensor and telemetry system that can be used in any type of sound environment to auscultate patient body sounds. In particular, the present invention relates to a modular auscultation sensor and telemetry system that comprises several interacting modules.
Auscultation involves the listening of body sounds such as, for example, cardiac, pulmonary, and Korotkoff (blood pressure) sounds. In a noisy environment, however, auscultation of such sounds can be exceedingly difficult if not impossible with current state-of-the-art stethoscopes.
FIG. 1 illustrates an example of a state-of-the-art, mechanical type, stethoscope 10 typically used to listen to the body sounds of a patient. The state-of-the-art stethoscope 10 essentially comprises a bell-shaped acoustic coupler 12 that is placed in contact with the skin surface 14 of a patient in, for example, the thorax region, in order to detect body sound signals S that are broadcast through the skin surface 14. Stretched across the bottom of the acoustic coupler 12 is a diaphragm or membrane 16 that aids in transmitting the sound signals S to the interior 17 of the acoustic coupler 12. Coupled to the interior 17 of the acoustic coupler 12 is a hollow, air-filled transmission tube 18 which transmits the sound signals to a pair of spring-loaded, air-filled, metal tubes 19. Attached to the ends of each of the metal tubes 19 are ear canal adapters 20 that can be positioned in the ear canals of a user. The acoustic coupler 12 in combination with the diaphragm or membrane 16, the transmission tube 18, metal tubes 19, and ear canal adapters 20, collectively function as a mechanical microphone or transducer, an amplifier, and sound transmitter. For example, the coupler 12 detects the signals S that are broadcast through the skin surface 14 and amplifies the signals, the transmission tubes 18 and 19 mechanically transmit the signals via a column of air within the tubes 18 and 19 to the ear canal adapters 20, and the adapters 20 emit a sound signal to the listener.
In addition to detecting the desired body signals S, the stethoscope 10 will also detect airborne noise N.sub.A and surface motion noise N.sub.S, that can occur when the coupler 12 moves along the thorax surface 14. Furthermore, sounds coming from the body may also include unwanted noise N.sub.B, for example, sounds produced when the patient moves his or her muscles or ambient sounds that are transmitted through the patient to the stethoscope 10.
The airborne noise N.sub.A, surface motion noise N.sub.S, and body noise N.sub.B can be much louder than the body signals S. For example, in ambulances and various aircraft used to transport critically ill or seriously injured patients the sound pressure levels, measured in decibels (dBs), may be in the range of 80 to 120 dBs. In particular, the sound level can be in the range of 90 to 100 dBs in a civil helicopter, 90 to 120 dBs in a military helicopter, and 80 to 85 dBs in an ambulance. The intensity of breath sounds of a healthy adult, however, is approximately in the 22 to 30 dB range. In such an environment it would generally be impossible to hear the breath sounds of a patient with a typical state-of-the-art stethoscope.
Some state-of-the-art stethoscopes may include two transmission tubes constructed from a polyvinylchloride material. In addition, the ear canal adapters of some state-of-the-art stethoscopes have been modified to form an improved audio seal with the ear canal in order to eliminate some ambient noise that the user may directly hear. Still other state-of-the-art stethoscopes may employ a small battery-operated, electronic amplifier in the transmission tube in order to amplify the signals detected by the stethoscope. The amplifier, however, increases the level of all sounds detected by the stethoscope including airborne noise N.sub.A, surface motion noise N.sub.S, and body noise N.sub.B. In general, the sensitivity of the state-or-the-art stethoscopes, including those with battery-operated amplifiers, are considered to be inadequate, particularly in a noisy environment.
The present invention, therefore, seeks to provide an effective auscultation system that optimizes the signal to noise (S/N) ratio by decreasing the level of the noise N reaching the listener's ears.